Touch display apparatuses can operate under a touch period and a display period. The touch display apparatus includes a plurality of scan lines and a plurality of data lines. The scan lines are perpendicular to the data lines to define a plurality of pixel units. The touch display apparatus further includes a gate driver for driving the scan lines, a source driver for driving the data lines, and a time controller for controlling the gate driver and the source driver. The gate driver includes a shift register. The shift register includes a plurality of cascade-connected unit circuits. Each unit circuit receives a clock control signal, a set signal, and a reset signal, and outputs a pulse signal as a scanning signal to one of the scan lines. Each unit circuit includes a plurality of transistors, a driving transistor, and at least one capacitor, in which the at least one capacitor is electrically coupled between a drain electrode and a source electrode of the driving transistor. The driving transistor outputs a signal synchronous to the clock signal as the scanning signal when turned on. The touch period is inserted between any two display periods. During the touch period, the unit circuit of the gate driver stops outputting the scanning signal, and the driving transistor remains on. A voltage of a gate electrode of the driving transistor may decrease based on a leakage current and the capacitor, and the voltage for turning on the driving transistor increases. When switching into display period from the touch period, the voltage outputted by the unit circuit is lower than a specified voltage, thus abnormal image is displayed during the touch period. Thus, there is room for improvement in the art.